There is substantial interest in the petroleum industry for converting heavy hydrocarbonaceous feedstocks to lower boiling liquids. One type of process suitable for hydroconversion of heavy feedstocks is a slurry process using a catalyst prepared in a hydrocarbon oil from a thermally decomposable metal compound catalyst precursor. The catalyst is formed in situ in the hydroconversion zone. See for example, U.S. Pat. Nos. 4,226,742 and 4,244,839 which are incorporated herein by reference.
It is also known to use such catalysts in hydroconversion processes in which coal particles are slurried in a hydrocarbonaceous material. See, for example, U.S. Pat. Nos. 4,077,867 and 4,111,787.
Further, U.S. Pat. Nos. 4,740,295 and 4,740,489, both of which are incorporated herein by reference, teach a method wherein the catalyst is prepared from a phosphomolybdic acid precursor concentrate. The precursor concentrate is sulfided prior to final catalyst formation. This presulfiding step is taught to produce a catalyst having greater control over coke formation. The sulfiding agent in these two patents requires a hydrogen-sulfide containing gas, or a hydrogen-sulfide precursor. The resulting catalyst concentrate is used for hydroconversion of heavy hydrocarbonaceous materials to lower boiling products.
U.S. Pat. No. 4,151,070 teaches a two-stage slurry hydroconversion process in which the second stage is operated at more severe conditions than the first stage stage. The more severe conditions include higher temperatures.
The term "hydroconversion", with reference to a hydrocarbonaceous oil, is used herein to designate a catalytic process conducted in the presence of hydrogen in which at least a portion of the heavy constituents of the oil is converted to lower boiling products. The simultaneous reduction of the concentration of nitrogenous compounds, sulfur compounds, and metallic constituents of the oil may also result.
While there are various hydroconversion and hydrotreating processes which are commercially practiced, there still exists a need for process variations which will increase the level of conversion of higher boiling products to lower boiling products, particularly high quality liquid products.